Stock material or miscellaneous articles – Hollow or container type article – Shrinkable or shrunk
Patent
1988-11-09
1992-04-28
Seidleck, James J.
Stock material or miscellaneous articles
Hollow or container type article
Shrinkable or shrunk
215 122, 428 357, 428200, B65D 2536
Patent
active
051088053
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a multilayer decorative composite for packaging, particularly of food products, whose rigid or semi-rigid multilayer walls are made by thermoforming, the external layer of the packaging being of thermoplastic material and being overlaid on all or a portion of the composite by thermofastening.
Such packages are generally made by treatment machines of the form-fill-seal type. The mono or multilayer thermoplastic polymeric or copolymeric sheets are thermoformed. During this thermoforming, which is conducted at a temperature of about 150.degree. C., the decorative composite adheres to the external surface of the outer walls of the packaging thanks to overlaying. When the rigid or semi-rigid walls of the packaging are very thin, which is to say between 100 and 200.mu., the packaging cools very rapidly, does not contract, and the paper remains intimately bonded to the walls. These very thin walls may be single layer (for example a layer of polystyrene) or multilayer (for example polystyrene/barrier layer/polyethylene). The decorative composite itself may be constituted either by bleached layered kraft paper of 90 to 115 g/m.sup.2, whose layered surface is adapted to be printed, the other face being covered by a thermofusible (hot melt) of 10 to 18 g/m.sup.2 thermobonded to polystyrene, either of an aluminum composite, for example 7 to 9.mu., bonded to kraft paper of 80 to 115 g/m.sup.2, the aluminum surface being adapted to be printed and the kraft paper being covered by a thermofusible (hot melt) thermobonding to polystyrene.
At present, when the walls of the packaging are very thin, the decorative composite also stiffens the whole of the package.
It had been proposed to provide packages having walls much thicker, up to 700.mu., or even more. This is necessary, for example, for packages in the form of a tray adapted to be reheated in microwave ovens and containing for example cooked dishes or the like. The walls should be thick, so that the packaging keeps a certain shape during cooking. They are normally multilayer, the external layer being of thermoplastic material such as polypropylene among others. Moreover, the thick multilayer walls of course have the characteristic of remaining hot for a long time and of contracting upon cooling.
Thus, the conventional decorative composite of kraft paper or of aluminum/kraft paper thermosealed to the thermoform progressively separates from the packaging during cooling, either after thermosealing or after reheating of the package, for example in a microwave oven. This partial delamination of the composite accordingly results in the formation of blisters at the level of the decoration and of course detracts from the overall appearance of the decoration and therefore of the packaging (see FIG. 1 of the accompanying drawings).
Moreover, the kraft paper-base decorations have a very low resistance to humidity and problems of blistering frequently arise after storage in a cooled chamber, or after contact with water during cleaning.
Finally, these decorations covered by a substantial layer of thermofusible (hot melt) material frequently leave a deposit of this product on the treatment machine, which requires frequent stoppage for cleaning.
The general problem solved by the present invention therefore consists in providing a decorative composite, adapted to be applied on all or a part of the rigid or semi-rigid thin walls of the packaging whose external layer is of thermoplastic material, and which has a coefficient of contraction such that it will be remain intimately bonded to the walls of the packaging during contraction of these latter due to any kind of cooling, for example after thermoforming or after placing the package in an oven, so as to avoid blisters at the level of the decoration and to improve the general appearance of the packaging assembly.
Moreover, this composite should have high resistance to humidity and avoid frequent stoppage of the treatment machine for cleaning.
The invention thus has for its object a multi-layer decorative
REFERENCES:
patent: 4190168 (1980-02-01), Jacques
patent: 4608284 (1986-08-01), Roales
patent: 4755403 (1988-07-01), Ferguson
patent: 4844957 (1989-07-01), Hoffman
Raymond Morin, S.A.
Seidleck James J.
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